template< class F > constexpr auto and_then( F&& f ) &; | (1) | (since C++23) |
template< class F > constexpr auto and_then( F&& f ) const&; | (2) | (since C++23) |
template< class F > constexpr auto and_then( F&& f ) &&; | (3) | (since C++23) |
template< class F > constexpr auto and_then( F&& f ) const&&; | (4) | (since C++23) |
If *this contains an expected value, invokes f and returns its result; otherwise, returns a std::expected object that contains a copy of error().
If T is not (possibly cv-qualified) void, the contained value (value()) is passed as an argument to f; otherwise f takes no argument.
Let U be:
T is not (possibly cv-qualified) void: std::remove_cvref_t<std::invoke_result_t<F, decltype(value())>>; std::remove_cvref_t<std::invoke_result_t<F, decltype(std::move(value()))>>; T is possibly cv-qualified void), std::remove_cvref_t<std::invoke_result_t<F>>. The return type is U, which must be a specialization of std::expected, and std::is_same_v<U::error_type, E> must be true.
true
true
| f | - | a suitable function or Callable object that returns a std::expected |
The result of f or a std::expected object that contains an error value, as described above.
| Feature-test macro | Value | Std | Comment |
|---|---|---|---|
__cpp_lib_expected | 202211L | (C++23) | Monadic functions for std::expected |
|
(C++23) | in-place construction tag for unexpected value in expected (class) (constant) |
|
(C++23) | returns an expected containing the transformed expected value if it exists; otherwise, returns the expected itself (public member function) |
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